Jspout

Hi folks, Decided to get rid of the 305 pig in my 1990 Iroc convertible and put a 92 corvette LT1 motor into her. I also had my 700r4 rebuilt with all the upgrades and installed a posi rear end 3/73 with the disc brakes. I have been documenting this motor swap and will share the details and photos with you of the process along the way. As soon as I figure out how to upload photos, I will get this thread rolling!

BlueZee28

iTrader: (30)

Who is making your harness?

Jspout

A fellow camaro enthusiest friend of mine is doing the harness. He is combining the 2 harnesses. Not a job I would be able to do, seems he is about 2/3rds the way done and we will be installing it early next week. It looks great so far and he seems confident in what he's doing. If all works out and he wants to, I will pass his contact info along!

Jspout

Here she is, before the install. This is a 1990 Iroc convertible, so pulls up on the vin numbers. However, this car had a 305 TBI motor option??? Strange things going on in that year being the last year of the Irocs. In my research, the 305 TBI was an option on the convertible Irocs in 89 and 90, so....

Jspout

This is the original 305 TBI motor in this car. A smooth running engine, will run forever, but a gutless wonder and gas hog too. I ended up trading this motor for a nice Taurus "Barretta" style 9mm pistol. I was happy with the trade and he and his brother came down to Branson and helped me pull it out. We had it out of the car in 2 hours! Good riddens! Not sure why you'd want a 305 when there are so many 350s out there.

Jspout

The empty engine bay, she is out! No real issues getting her out. lots of stuff to disconnect, I just ended up cutting the Y pipe as it would get in the way pulling it out. I was alittle concerned as I have a brand new windshield on it, but the 3 of us handled it no problem.

Jspout

Last fall I bought a 1992 Corvette LT1 engine with 72K miles from a local guy for $800. He intended to put it in a 60s model Impalla, but decided to buy a crate 383 roller instead. I think he got a little freaked out on the LT1 change over and expense of it. The engine was quite dirty and sat in his garage for a few years. Had a 700R4 attatched to it, however was not the original transmission. The harness dictates it had a 6 speed behind it. It did not come with a computer, so that was my first adventure! The 1992 LT1 is the red headed step child to corvette engines. Was the first year of the LT1 even before the 4th gen camaros and firebirds. This engine is not the same as the 4th gen LT1s. It is rated at 300 HP stock and everything mounts to the right side of the engine. and the fuel comes in on the left. Turns out I had to find a specific computer and eprom for this engine. PITA! The nice thing about the 92 Vette LT1 it is a speed density system and you can run any earlier desired transmission behind it, as the transmission does not have to be computer controled. After months of scoping out ebay I finaly found a good computer with the correct eprom chip installed for $175. These computers cannot be flashed, so I had to send it out and have a chip programmed with all the neccessary deletes, VATS, emmissions, etc. That cost me $75. I ended up picking up another remufactured computer as a backup. That was $200. So, yes there are expenses involved in this swap, but I knew that going in. This is the engine I wanted in that car! and you will see why in my next posts.

Jspout

I spent a couple of weeks cleaning up this LT1 and painting it.

I pulled the water pump off and I had another water pump from a 93 4th gen camaro I used to have in good condition. This water pump will work out great as it has the extra spouts for the heater core on the Iroc. I painted it red and put new gaskets on it. I also pulled the Vette exhaust manifolds off the engine as they would not work on this car. The manifold ports streight downwards in the middle and the engine mount frame is right there. Plus, the camaro engine mounts are larger than the Vette and hit the manifold. I wanted headers any way. I also removed the throttle body and cleaned and painted it too and found a cool Iroc Z plate for the top of it. Removed the valve covers, stripped and painted them red too.

Jspout

I decided to go with the 700R4 transmission. I found a guy local that rebuilds those and had a couple people recommend him and his work. For $350 he rebuilt the transmission and did all the upgrades and updates. No extra charge put corvette servos, heavy duty springs, a mild shift kit and some other technical jargen stuff I did'nt even understand. I also bought a heavy duty torque converter with the kevlar bands. That was $140 and the correct Detent cable for the LT1 $25. I also found a guy on CL parting out a 92 Corvette and bought all the missing needed parts off it. I got a new AC compressor, flex plate, and fuel pump from him. I pulled the rear end out and exhaust so I could get the gas tank out and replace the 3rd gen fuel pump. This was nessessary as the TBI pump is inadequate for the LT1. The rear end removes pretty easy, I was shocked. Had it out in an hour. I had a new posi 3/73 rear end to install any way with the disc brakes. I am excited to get rid of those worthless drum brakes!

Jspout

The gas tank on the 3rd gen came out remarkably easy, just had to remove the heat shields and the fuel lines, the spout just sticks up there nothing to unbolt but the 2 tank straps. The pump removal was fairly easy too and the corvette pump plugged right in, no hastles, same plug. got everything reinstalled. The rear end is a little trickier to install than removing. i have a motorcycle jack that really helped in the process. I think the posi rear end I installed is from a 4th gen as was about an inch wider on each side, which I like the look. I mounted the newly built 700R4 to the LT1. Put 1 quart of trans fluid into the the torque converter before installing so that it wont spin dry. When installing the converter, I put it on the trans first all the way in so the slots lined up. then mounted the transmission to the engine, while on the hoist. then from the bottom of the engine I slowly backed the converter to the flexplate in incriments. this important so the converter doesnt **** at an angle and jack up the seals. turn the cranks by hand and tighten the bolts a little at a time untill it is tight to the flexplate. Engine is ready for installation!

Jspout

the engine install. Probably should have had some help, but installed it by myself. Used a jack for the transmission and jacked it slowly as I lowered the engine. the mounts lined up perfectly, no real issues. I was a little concered the accessories and brackets on the right side of the engine would fit as there is a lot going on over there on that side, but it fit like a glove. VERY PLEASED!

Jspout

If you click on the pictures you get the full sized ones.

Jspout

Here she is, this motor seems right at home in this car!

Jspout

This is where I am at now, after some extended research on this forum and trial and error, I found a set of SLP shorty headers 30005 that not only fit the 3rd gen engine bay, but the D ports on the LT1 too and does not interfere with the spark plugs or AC bracket. They were a little pricy(discontinued), but are quality and look awesome too! Searched the entire country for a matching SLP Y pipe..... Found one in Detroit Mi. The only problem the guy would'nt separate from the headers or ship them. Fortunately, I have a buddy in michigan that lived close enough to get them for me and ship them. Needless to say... I HAVE AN EXTRA SET OF SLP HEADERS 30005 FOR SALE $300 if anyone is interested. They are worth the price and good luck finding another set. They are perfect for this LT1 swap! I will be installing the Y pipe and the wiring harness this next week. I am no expert and am learning as I go, so any advice would be helpful. I see the light at the end of the tunnel!

86T/A_Ram_Air

Subscribed!

Tinbender59

dude You are my hero. I will be sending a pm on the headers, I have a 95 LT1 with 40k on it; that I picked up for $700 as a spair for my LT truck conversion. you really need to look at it. I dumped the Opti-no-spark. http://www.gmtruckcentral.com/articles/lt1swap.html I will be dumping the Opti again, but looking at doing something like the LS series cam sensor, on my 91 Vert.

ROCFATHER

Awesome dude! Waiting to see how she runs! I'm sure its gonna be a big difference from the 305!

Jspout

We are getting close to getting her fired up! I got the Y pipe and SLP headers in the mail. took me a whole day to install them. Now I know why they charge so much for Y pipes as they can be a royal PITA! This Y pipe came off a third gen Firefird. I discovered there are some slight differences in the frame from the thrd gen Camaro and a major difference in the oil pan from the 92 corvette LT1 and the 4th gen Camaro LT1. The cross pipe was hitting the oil pan as I now know the Corvette oil pan stays deep further back to the rear. To those of you making this swap with the corvette LT1, I recommend swaping to a 4th gen oil pan. It leaves more room for the Y pipe. Needless to say, I had to flatten out the Y pipe some with my trusty sledge hammer to fit under the oil pan and on the bend right before the Y the pipe was hitting the frame some too. I did it by myself, however a third hand would have made it a whole lot easier and faster. The collectors were off about 1/4 inch or so so I had to stretch them apart a little with my pry bar as I was tightening the bolts. I got a real bad leg cramp while under the car and had the pipe accross my chest and could'nt get out! Crap! LOL. Another issue, the high flow cat connected to the Y pipe exits 3 inch pipe and my exhaust is 2 1/2 inch. ARRGH! At least I got the Y pipe in so we can get her started. I will deal with the exhaust next week! I will post pics later.

jnman

Subscribed!

Jspout

Yesterday was the big day, I was going to get her fired up! been working on her all week getting things tightened up on her, hoses, belts, intake, battery, etc. Been to the auto parts store every day, I'm sure I raised Oreileys stock some this week by myself. Mike continued working on the instalation of the Wiring harness. The Harness looks great and he clearly knows extensively about this engine. He has expressed interest in doing more harnesses.

So, we have not yet added fluids other than oil, just in case I have to pull it back apart and change the optispark. Cranked it over and..... nothing, not even a spit. Mike and I went down the line. We had good fuel pressure, the new pump was clearly working(one less worry), we hooked up the test light to the injector harness and were clearly getting a pulse while cranking. we tested the electrical contacts to and from the Coil. It was a brand new coil, so eliminated that, but no spark from the opti. CRAP! Had to be the opti, so like a mad dog took her back apart, had it stripped down to the opti in less than an hour. Tried another opti and it did not spark either. OK, now what. This obstical is what turns people off to this motor. Not me, we have to be closing in now. I researched on some other threads of the "No spark" issue. Many times turned out to be the little pig tail harness to the Opti. Even though the it tested good, I had Mike remake that section of the harness. OK, tested the opti and we now had spark, Yea!! But, it would still not start. So the nightmare things that go through your mind, bad computer, installed the fuel pump wrong, etc. So we had fuel pressure, had a fire on the injectors, had a spark from the opti. It should be running, unless the rail is clogged up. So, i had mike spray some started fluid in the intake and..... This time she roared to life sounded like a wild beast! but only for a brief second. In that brief second, we both had a sigh of relief, but still meant no fuel was passing. Turns out We both neglected testing the injectors, many were not functioning. So, now had to order some injectors. Plus I need a throttle body for an automatic. I am at a stand still, till i get the parts, but got her to fire, I am happy.

Jspout

Got her back together ready for the new injectors. I still will need a new throttle body for the DT cable hook up before I can get her out on the road. My goal is the Branson car show in 2 weeks. Still possible, I guess. I had to do a couple fabrication mods today. took my old computer tray and made a custom tray for the new LT1 computer. I placed it in the driver side corner of the engine. It fit nicely and is far away from the headers. I put a piece of insulation and wraped the computer with a carpet remnant I had to protect it. I thought I would share a couple other mods too the fuel lines came in one small and one large fittings but there were 2 large connections on the LT1 lines. I cut the LT1 lines and used some compression fittings to size down the one side. A mod you will have to do if you do this swap.Also I had to install a MAF sensor into the new airbox I got for it. Added 4 qts of trans fluid to the rebuilt transmission. I already put one in the Converter, so about 6 to go when I can get her in gear. Filled the PS fluid and radiator. another trick I learned on my 4th gen... drill a small hole in your thermostat, gets rid of the bleading headache in these motors. I stayed with the 3rd gen fan as it pushes more air then the 4th gen duel fans.



Should have her running in a few days.

RumbleZ

Yeah, I definitely would not have guessed 5 of 8 injectors were not working at all I'll check that sooner on the next one for sure. I've never seen that many dead injectors on same engine.

The hole you added to the intake was for the IAT (Intake Air Temperature) Sensor, you don't have a MAF.

Anyway, Here are the few pics I took of the harness at different stages of the process. I had a few pics not turn out, so there's not many.

Here's the factory '90 TBI harness stripped down (sorry, no before pic it ended up being really blurry)


factory '92 Corvette LT1 harness before


LT1 harness stripped down and now joined with C207


getting ready to join the rest of the 3rd gen harness to the LT1 harness


Just about ready to install, with the pinouts and custom diagrams

RumbleZ

One thing I didn't see that's probably worth mentioning is the passenger side O2 sensor on those SLP headers interferes with the Corvette starter. I'm not sure if the fbody starter would have been any better, but the long metal casing had to be removed from the top of the O2 sensor to get the starter to bolt up.

Jspout

Today put a good set of injectors on her, filled the radiator, and BOOM she fired right up and sounds great just like she's supposed to! I have been doing cartwheels all day since. Sounds beastly! The exhaust is'nt hooked up yet. I found a throttle body for the automatic DT cable online. Cost me some money but is remaufatured and bored to 52mm. Should be cool, then I can break in the transmission and get her on the road. hopefully they ship fast. I will post a video somewhere and share with all yall.

Jspout

Progress report: Still working out the bugs, but I am back on the road! I had the exhaust welded last week, sounds pretty good through the high flow cat and the flowmaster, but not quite as bad *** sounding as the Borla on my 93 Z28. I also took her to a mechanic friend of mine to help adjust the Detent cable, was'nt shifting quite right, and I was just taking wild stabs in the dark. I must admit, it is like driving a different car now, and it is taking a getting used to. I have a mild shift kit installed so the shifts are strong and agressive. I can no longer drive it like a granny car. The posi 3/73s are way different too. The motor so far runs smooth, don't burn no oil, fires up quickly, don't overheat. I am watching it like a hawk untill I am satisfied of no issues. The alternator crapped out, but I kinda knew it would, changed that out. I still have to pull the ebrake cables off my other rear end, these ones from the posi are shorter and have different anquor points. Hopefully they will work. I have a new vinal top to install, I probably will get to that next week or so. I think I will get a car cover and get used to covering it that way. for a while any way. I think maybe next year I will put true duels and get it dyno tuned. I will post pics soon.

Jspout

Update on the LT1 swap. Sorry folks, been a while since I posted. Well, I have put about 1500 miles on her since the swap and is running strong. I installed a B & M megashifter and what a huge difference! It really solved all of my shifting issues. The new Transmission rebuild with shift kit has mellowed out and shifts nice now. The B & M was a jigsaw puzzle to install, but gives you precise fast shifting with a cool ratchet style shifter. It is vertually error proof, so you can fly through the gears with ease and without worry. Well worth the $200 I paid for it. One issue I am haveing and maybe someone can help me, the gas tank is building up preasure and seems to pull the gas back into it over night as it sits. I do have the corvette fuel pump installed in the tank. I have gotten used to relieving the pressure when I park it by losening the gas cap, but would like to remedy this issue as I have to turn the key on 4 or 5 times to get the fuel delivery to the injectors. I installed a new top on the Convertible and also got her to pass inspection and tagged. With all the changes I made to this car, I am pleased and relieved I got the tags. The next area that needs attention is the front brakes. They pull to the left when I hit them hard and even at a stop if I tap them the steering wheel turns a bit to the left. Stuck or bad Caliper? I appreciate the help and advise you guys have given throughout the proccess. Thanks, Lance P.S. I still have a nice set of SLP 30005 headers available. Hard to find but what you need for this LT1 into 3rd gen swap.

Thirim

Kinda ressurecting the dead here but I'm curious as to how you bolted on the accessory bracket? I see 2 holes that line up on the front of mine and a series of rods and brackets of the back that line up to nothing?

Thirim

ok based on your pics I figured the bracket out, 3 holes lining up, I'm good with deleting the bars behind..
How did you make the PS pressure hose work?